Abstract:

Dynamic loading due to earthquakes alters the stress-strain properties and strain distribution in steel reinforcement. Past research on dynamic load effects has been under constant strain rates, and the applicability of results to variable strain rates caused by earthquakes is uncertain. In the study presented herein, the effect of variable strain rate and distribution of strain along the length of steel bars were studied experimentally. The specimens were ASTM Grade 60 with #3, #8, and #11 sizes, and the strain rates ranged from 0.0001 to 0.1 strain per second. The analysis of data showed that the rate of change in strain rate (second derivative of strain) is an important factor. The data also revealed concentration of strain at higher strain rates. Based on the results new simple equations to estimate the yield and ultimate strength of the bars were proposed and compared with other available data.